Effects of alternating current (AC) frequency on corrosion behavior of X80 pipeline steel in a simulated acid soil solution

The effect of frequency of the applied alternating current (AC) on corrosion behavior of X80 steel in an artificial liquid aiming to simulate the acid soil medium of Yingtan area was studied by means of electrochemical measurement, immersion test and surface characterization technique. The results showed that with the increasing AC frequency, the corrosion rate and the corrosion degree of X80 steel decreased gradually. The corrosion product of X80 steel under the applied AC was loose with many cracks thus could not offer proper protection to the substrate. The offset of corrosion potential of X80 steel decreased as the AC frequency increases. With the increase of AC frequency, the oscillation amplitude of anode and cathode polarization curve gradually receded. In the range of the test frequency, the applied AC to X80 steel not only induced the increase of the current density for both anode and cathode, but also the change of cathode reaction from mixing control to activation control.